Liver transplantation has become the treatment of choice for patients with advanced liver disease. In these patients, kidney dysfunction often contributes significantly to post-transplant morbidity. An accurate measurement of kidney function is therefore important and will allow identification of high risk patients who may benefit from modified immunosuppressive therapies. Clinical evaluation of kidney function in patients with advanced liver disease is not always straight forward. Although commonly used in clinical practice, creatinine (a substnce of musclebreakdown excreted by the kidneys) clearance and urea (a substance produced in the liver and excreted by the kidneys) in the assessment of kidney function are fraught with pitfalls. Prediction of kidney function from various formulas using serum creatinine and factoring for age, gender and weight are biased and imprecise. The current pilot study will evaluate the comparative accuracy and cost of two commonly used formulas (Cockroft-Gault and modified Wasler) and clearances of creatinine and urea to predict kidney function. Clearance of radioactive I125-iothalamate will be used as a gold standard.